The research proposed here concerns N-methyl-D-aspartate receptors (NMDARs), brain proteins that are activated by the neurotransmitter glutamate and that mediate communication between neurons. NMDARs are required for many normal brain functions, such as memory formation, and also are involved in many human diseases, including Alzheimer's Disease and schizophrenia. The long-term objectives of the proposed research are to understand at a deep level how NMDARs function, what they look like, and how drugs that bind to them can either improve or exacerbate nervous system diseases. A powerful combination of techniques will be used: recording of the electrical activity of NMDARs in neurons within brain slices and from cells modified to express specific types of NMDARs; use of molecular biological techniques to change the chemical makeup of receptors and investigate how the changes affect receptor function; recording of the electrical activity of single receptors; use of computational techniques to create models of the physical makeup of receptors to improve understanding of their structure; use of other computational techniques to create functional models of receptors to improve understanding of how they work. Several specific research goals are proposed. The first is to investigate how NMDAR subunits interact with each other. NMDARs are composed of four separate subunits that work together in a tightly integrated manner. Some regions where subunits interact with each other have been studied, but others have not. In the proposed research, the functional role of a newly-discovered region where subunits interact will be studied. The second goal is to develop a better model of the structure of NMDARs based on knowledge of the structure of related proteins and on computer simulations. Accomplishing these first two goals together will greatly improve understanding of the basic mechanism by which NMDARs mediate neuronal communication. The final goal is to understand how drugs that bind to NMDARs work. One drug that will be studied is used to treat Alzheimer's disease, whereas the other drug causes normal humans to display the symptoms of schizophrenia. Both drugs bind to NMDARs, but they have very different effects. The goal is to understand the important differences between the actions of the drugs to provide insight into the drug characteristics that allow one to help Alzheimer's disease patients, and the other to mimic schizophrenia.